Achieving good shrink wrapped packages is an art in lieu of a science. Many factors will effect how a
package looks exiting the tunnel. ―Wrapping‖ is often used interchangeably with ―packaging.‖
Unfortunately, because even packaging professionals and customers use different terms to describe
the same wrapping or packaging processes, it’s not always easy to know what you—or they—are
talking about. But here are a few terms to get you started.
Overwrapping: Synonymous with diamond-fold wrapping, tuck-and-fold wrapping, gift-box wrapping,
cigarette wrapping and bundle wrapping. Overwrapping is a process in which a box-shaped carton,
tray, bundle, etc. is wrapped and sealed in any of a variety of relatively stiff, single- or multi-ply web
materials including clear, printed and/or metallized polypropylene (PP), cellophane, paper, glassine,
waxed paper, aluminum foil or metallized paper/BOPP (biaxially oriented polypropylene). The end
result looks like a ―gift wrap,‖ with one long seam located either on the bottom or side of the package
and each end of the package neatly ―tucked, folded and sealed.‖ The first tuck-and-fold machines
were designed in the 1920s by the original Package Machinery Company. Tear tape is often used as
an easy-open feature. Overwrapping machines are built in elevator, in-line, turret or rotary styles.
Examples of overwrapped products include cigarettes, Easter ―PEEPS‖ candies, CDs/DVDs, frozen
food cartons, cartons/boxes of tea.
While we’re on the subject of overwrappers, here are three things you should never say when in the
company of expert on wrapping machinery:
“You can overwrap with soft [polyethylene-based] films.”
This is a common misconception.
Such films are too soft and have too much ―give‖ to be run on
conventional wrapping equipment.
“Overwrapping, like shrink wrapping, needs an external heat source/tunnel to shrink the film in order
to have a good wrap.”
Again, not true.
Most BOPP (biaxially oriented polypropelene) exhibits little shrink (5 percent to 13
percent on special films). Heaters ARE integral to overwrappers, but they aren’t used to shrink the
film—they’re used to seal the endseams of the wraps.
"Overwrapping means the same thing as shrink wrapping, flow wrapping and diefold wrapping.”
Wrong! Each of these is a distinct wrapping process.
This process—not widely used anymore—achieves an overwrap on a soft,
non-box shaped product by enveloping it (often placed on a card or U-board) in film and sealing the
bottom. The film forms either a box or circular shape around the product via a ―die-box‖ in the
machine’s elevator section. Limited application of heat (only to the bottom seal) gives the product a
tuck-and-fold appearance that doesn’t need side sealers and won’t be crushed by the machine or
melted by its heat. Diefold wrapping has been replaced by the faster, more hermetically sealable
flow-wrap process. Reese’s Peanut Butter Cups once were diefold-flow-wrapped with two cups seated on a
chocolate-colored U-board in cohesive film (which requires no heat for sealing). The process is still
used for some Reese’s Peanut Butter Cup SKUs. Also, ―homemade‖ cookies whose manufacturers
are going for the ―baked-like-grandma’s‖ look still use the diefold wrapping process.
Synonyms include ―doughboy‖ wrapping (Doboy is a widely used brand of flow
wrapper), fin-seal wrapping, crimp-seal wrapping and pillow-pouch wrapping. Flow wrapping is a
horizontal-motion process in which product of any shape is wrapped in clear/ printed PP film. The end
result is a flexible package with a non-lap type seal on the bottom and crimped end seals. Both the
process and films in flow wrapping are quite different from overwrapping. Flow wrap BOPP films; for
example, need only to seal to themselves. Overwrap films need to seal to themselves and the other
side. There are zillions of products that are flow-wrapped. Think wipes, tissues, vending machine
candy bars, etc.
Here are a few close relatives of shrink wrapping (though not exact synonyms):
L-seal wrapping, stretch-seal wrapping, bundle wrapping. Shrink wrapping is a process that uses
relatively soft polyolefin film in which a loose sheath of film is created around the product, often
sealed on two sides. The loosely sheathed product passes through a heat source, which shrinks the
film to the dimensions of the product. The result is a very tight wrap, conforming to the product shape,
often with a ridge of plastic around the perimeter of the product or gaps in film on either end. Shrink
wraps are typically stronger than overwraps and the machines are inherently very flexible. The
downside is that shrink wraps can be less attractive than overwraps. And operational costs are often
higher because of film waste and energy consumption. Note: ―stretch‖ and ―shrink‖ obviously don’t
mean the same thing. Stretch wrappers, a popular choice for wrapping pallet loads of products,
achieve tight wraps by expanding the stretch film—rubber-band–like—before enveloping the product
and letting the film return to its original size.
The shrink film market is comprised of three basic categories:
1. Polyvinyl chlorides (PVC),
3. Polyethylene’s. Shrink polyethylene is not typically included in the competitive
polyolefin category; ―poly‖ lacks the clarity, gloss and the tight
second skin polyolefin’s provide. These attributes are critical
for retail appeal. Poly’s shrink in the ―cooling‖ period of the
The polyolefin ―family‖ consists of films made from polyethylene or polyethylene and polypropylene
copolymer resins. Suppliers are Syfan, Cryovac and Clysar.
PVC shrink films derive their properties from additives, which are primarily plasticizers. As these films
age, the plasticizers migrate and the film reverts to its brittle state, turning to a yellowish color. Also,
PVC films tend to be temperature sensitive, developing a tendency to shatter and split at cold
temperatures (below freezing), and ―shrink-back‖ and/or block when exposed to high temperatures
over a period of time. The color may also change to yellow when exposed to heat (such as being
stored in a non-air-conditioned warehouse over the summer).
PVC (Polyvinyl Chloride)
A thermoplastic material composed of polymers of vinyl chloride; a colorless solid with outstanding
resistance to water, alcohols and concentrated acids and alkalis. Compounded with plasticizers, PVC
yields flexible film widely used in the manufacture of clothing and packaging films
A generic term used to describe ethylene and / or propylene-based films.
A simple thermoplastic polymer of ethylene. Each molecule consists of hundreds / thousands of
carbon atoms. The length molecules and the amount of side branching determine the characteristics
of the film, i.e. LDPE, LLDPE, HDPE, etc. These films vary in clarity and are used primarily in the
industrial segment or for overwrapping trays of products. With the introduction of new resigns, shrink
poly’s are gaining in popularity.
A thermoplastic polymer of propylene. Polypropylene materials are generally oriented, heat-set (OPP)
materials which do not shrink
FILM SEALING SYSTEMS
Until recently, most sealing systems used a hot
wire in order to seal and cut-off the film at the
same time; now, a knife system has gained in
popularity on many models, due to its durability.
The wire or knife seals the film against a pad,
covered with Teflon tape to protect the pad. Time,
temperature and pressure are the three most
critical elements affecting the seal quality.
If the sealing head is not held on the film long
enough, the temperature is too low, or the
pressure is insufficient or uneven, the seal quality
will be poor, and/or won’t cut.
If the sealing temperature is too low, or the
pressure is insufficient or uneven, the seal quality
will be poor, and/or won’t cut.
If the sealing temperature is too high, the film may break just behind the seal. Following the impulse
sealing cycle, a cooling cycle allows the film to ―solidify‖ into a solid seal. This dwell time is critical in
order for a seal to hold.
PVC films require only heat in order to cut seal and cut. When run on a sealing system as previously
described, build-up of carbon char (black specs and flakes) will occur, and will need to be cleaned
from the sealing head on a regular basis; otherwise, the carbon will interfere with the sealing process,
and will look unsightly on the sealed ends of the package.
Since only heat is needed to form a PVC seal, some machines use a hollowed out bottom platen
instead of the foam pad; direct contact with the seal wire is eliminated. Other systems employ a much
thinner nichrome wire (.020‖ diameter vs. a standard .036‖ to .040‖ for polyolefin’s) against a hard
bottom sealing pad. This system is insufficient to create strong polyolefin seals. One other sealing
system designed for PVCs is called a Universal Sealing System. Despite the name, the hot knife is
typically too sharp to form a quality polyolefin seal. A rounded knife is better suited.
1. As seal bar close, film in direct
contact with the wire melts. Cutting
action is produced as film shrinks and
pulls away from each side of the wire.
2. Melted ends are compressed and
forced to fuse together between the
pressure face of the bar and the pad.
3. Seals are produced once film pulls
far enough away from the wire so
they return to a plastic state.
FILM SHRINKING SYSTEMS
Heat causes ambient air inside the bag to expand, while the bag shrinks.
Vent holes bleed-off excess pressure to prevent the bag from rupturing.
In order for proper shrinking to take place, polyolefin films and polyethylene films need an air
evacuation hole or multiple perforations. A bag formed with PVC film does not need ―artificially
created‖ air escape holes. Because of the make-up of PVC, the seal typically is full of small pinholes;
this is where the air escapes during the shrinking process. While this may seem advantageous (a
step can be eliminated), the small holes actually weaken the seal area. These holes are often located
near or in the package corners.
In order for proper shrinkage to occur, polyolefin film and polyethylene films must be exposed to the
correct temperature for the correct amount of time (which is controlled by conveyor speed), and also
be surrounded by the correct air velocity, or wind turbulence. The air allows the film to stand away
from the product, and a ―bubble‖ is formed around it. A good, even shrink should result when this
PVC films shrink readily when exposed to heat, and therefore air velocity is not critical. In the
marketplace there are low-end tunnels which have no settings to control air velocity (similar to an
oven) and you may find it difficult to achieve a good shrink
Films which have gone through an orientation step in manufacturing process, which shrink
significantly with application of heat.
Singlewound (SW) Film
A term used to describe a single layer of film wound around a core. It is generally used on automatic
Centerfold (CF) Film
This is a film that has been folded in half lengthwise and wound around a core. Centerfold Film is
usually used on slower, semi-automatic and manual packaging equipment which inserts the product
between the folded film and then heat seals the remaining 3 edges.
Natural Centerfold (In-Line)
An extrusion line used to produce the centerfolded film which slits the tubular film before it is wound
The process by which single-wound or flat film is mechanically folded for use on L-Bar Sealers.
A paper tube on which film is wound. Cores are furnished in 3" and 6" inside diameters; 3" is
standard. Cryovac uses 0.660 wall cores that weighs 0.2 lbs. per inch.
A term used to describe the thickness of film. One mil is equivalent to 1/1000 of an inch. 50- gauge
film is 1/2 mil thick, 100-gauge is 1 mil thick.
The direction that centerfolded film is wound on a core. Most centerfold film can unwind either from
top or bottom of the roll when viewed horizontally from the open side.
A single layer film extruded from one or a blend of several raw materials (Resins)
A film formed with multiple layers of similar or differing polymers. The purpose is to obtain specific
properties and characteristics.
Cross Direction (CD)
Film direction in the width of the film.
Machine Direction (MD)
Film direction in the length of the film as it comes off the roll or travels through the machine.
Film Manufacturing Process
Shrink Film Manufacturing
An extruder is constructed of a hollow cylindrical barrel which is fitted with heaters around the
exterior. A screw is fitted into this barrel which is driven by a motor. The polymer resin is loaded into
the rear of the extruder and conveyed through the barrel by the screw turning motion. As it travels
through the heated barrel the resin is compacted and melted. The screw then pushes the melted
resin through a circular die.
Coextrusion is accomplished by using multiple extruders that feed their melt through a feed block or
multicavity die. The die is designed so that the melt from each of the extruders are layered in the
The orientation of the molecules in a film plays an important role in its performance in both
mechanical and optical characteristics. The orientation of a film or tape can be made in either the
longitudinal direction or transverse direction in a simultaneous or two phase operation. The bubble
Polyolefin films uses is a method in which a tubular film or tape is heated after extrusion to the
orientation temperature and stretched by inflation with air between upper and lower sets of pinch
rollers operating at different speeds. The speed ratio of the pinch rollers controls the orientation in the
longitudinal direction, while the orientation in the transverse direction depends on the ratio between
the bubble diameter and the pre-inflation tape diameter.
Inflating the tube and stretching it equally in the longitudinal and transverse direction results in biaxial
orientation. Biaxial orientation improves the tensile strength, ball burst impact strength, flexibility, and
Preferentially (unequally) oriented film is usually produced by winding at a faster rate than the rate of
extrusion. This results in a film which is stretched more in the longitudinal direction then the
After orienting, the film is converted into finished goods by one of the following methods:
Singlewound Film: After collapsing the bubble, the film is edge ripped and wound into two large
Singlewound rolls called mill logs. These mill logs are then slit to the finished film widths.
Occasionally, mill logs may contain taped splices due to an interruption in the manufacturing process.
This is why customers may experience film splices in rolls.
Mechanically Centerfolded Film: Singlewound film is folded into centerfold film using specially
constructed frames over which the film is rewound.
What makes Shrink Wrap shrink?
Plastic shrink wrap has become such a huge part of our lives that we take it for granted. In fact, most
of us come in daily contact in one or another with this packaging method.
But how does it actual work? How does this ―stuff‖ work?
Well, it starts with the plastic polymer. Polymers are very long molecules. In fact the best analogy I
can use is that the plastic polymer is like a length of Christmas lights. As we all know, a length of
Christmas lights in its‖natural state‖ is all bunched up and tangled. In fact the more sets of lights you
have, the more they are all scrambled. Plastic polymers, like Christmas lights, are naturally scrambled
up and tangled.
However, shrink wrap film is manufactured so that the plastic polymers chains are oriented so that
they are un-naturally stretched out. These polymer molecules are now are longer by forcing them into
this awkward state. During orientation, the polymer is locked, or frozen, into its elongated state.
This straightened, longer, and oriented polymer shrink film can now be used to enclose any number
of products. The only thing left to do is add the special ingredient to create the magic of shrink. In the
case of shrink film the special ingredient is heat. Heat applied to the shrink film increases the
molecular motion of the polymers and causes the elongated polymers to recoil, or shrink back to its
natural random and disordered conformation.
Excess energy increases molecular motion (wouldn't you move if a fire were placed under your
backside?). Different polymers react to this heat shrinkage differently but 50% shrinkage from the
initial oriented size is not unusual. As in stretch film the tensile strength of the shrink film also
increases when heated.
This basic explanation applies to PVC, polyesters and polyolefin type shrink films.
Package (Film) Sizing
Film sizing should always be done by actually putting up some sample packages. However,
for estimating plain film sizing, there are some general guidelines which may be used.
Centerfold Film Sizing:
Sizing Formula for Manual, Semi-automatic, and automatic L-Sealers utilizing centerfolded film.
Automatic, Horizontal Form-Fill-Seal Equipment Film Sizing:
Singlewound Film Sizing and Formulas for high speed (50-200 packages per minute) Shrink
Side Seal Equipment Package Sizing:
Singlewound and Centerfold film sizing formulas for automatic side sealing equipment.
Shrink Film Problems and Solutions
Fish Eyes -
Shrink Film not shrinking completely.
Tunnel temperature is not high enough.
Tunnel Air velocity is not high enough.
Tunnel Conveyor speed is too high.
Crows Feet -
Shrink film shrinking too fast.
Air evacuation from shrink film containment is too fast.
Lower the amount or size of air holes to the shrink film
Dog Ear -
Shrink film not shrinking properly.
Shrink film Bag was made too large.
Tunnel temperature is too low.
Tunnel conveyor speed is set too high.
Tunnel air velocity is set too low.
Inadequate shrink film.
Heated air not exhausting.
No air evacuation holes in shrink film bag.
Not enough air evacuation holes in shrink film bag.
Burn Out / Burn Hole -
Shrink film overheated.
Not enough holes for air evacuation.
Tunnel temperature set too high.
Tunnel conveyor speed set too low.
Hot Spot -
Shrink film overheated.
Not enough air evacuation holes.
Tunnel temperature set too high.
Tunnel conveyor speed set too low.
Tunnel air velocity set too high.
Weak Seal -
Shrink film not sealing properly.
Seal temperature set to high.
Seal dwell set to low.
Seal pressure to low.
Seal pressure not even.
Sealing surface dirty.
Seal pad is worn.
Seal tape is worn.
Sealing cycle to fast.
Angel Hair -
Shrink film not cutting properly.
Sealing system temperature too low.
Seal pressure too low.
Shrink film not compatible with sealing system.
Bad Seal Position -
Shrink film seals not centered.
Sealer conveyor or table height set improperly.
Tunnel air direction set wrong.
Shrink film containment bag to big.
Shrink force overpowering product.
Tunnel temperature set to high.
Tunnel conveyor speed set to low.
Shrink film containment bag to small.
Shrink film has to much shrink force.
Shrink force overpowering product.
Tunnel temperature set to high.
Tunnel conveyor speed set to low.
Shrink film containment bag to small.
Shrink film has to much shrink force.
Shrink film tearing.
Air evacuation system tearing film.
Not enough air evacuation holes.
Sharp edges in film path.
Too much smoke after sealing shrink film.
Sealing system temperature set to high.
Not enough sealing pressure.
Dwell time set to low.
Film Splits At Center Fold W Film Splits At The Hole Punch H G X
Film Splits On Top Of Package H G X K L R N Smokes Excessively A B C E S U
Angel Hair A B C E F I J S V
Crows Feet R N X Q K
Fish Eyes K M N O Q
Dog Ears O M N X Q
Burn Holes / Hot Spots G L X R N
Erratic Shrink K M N X Q
Film Build-up On The Sealing Wire A B C E S V
Severe Ballooning Q X
Weak or Split Seals A B C D E F I J S T U V Z
Off Centered Seals Y Z
Seal Failure In Tunnel A B C D E F G I J K R N V Z Film Cannot Be Separated 1
A. Check and clean wire & wire insulation.
B. Check condition of sealing pad and Teflon tape. C. Check for even seal jaw pressure.
D. Check to make sure no tension is on the film during sealing. E. Make sure seal is made with minimum seal wire temperature.
F. Make sure sealing cycle is completed before sealing jaws are opened.
G. Check for location of air evacuation hole in package. (Hole should be to rear of package) H. Check hole punch for punch and die alignment or damaged die or punch.
I. Be sure magnetic hold downs are releasing at the same time.
J. Make sure the take away conveyor does not engage before the sealing jaws are opened K. Make sure the tunnel is functioning properly
L. Speed up tunnel conveyor. M. Slow down tunnel conveyor. N. Adjust tunnel air flow dampers. O. Use less film around the product P. Use more film around the product. Q. Increase tunnel temperature. R. Decrease tunnel temperature. S. Increase wire temperature. T. Decrease wire temperature. U. Decrease dwell time. V. Take off Teflon sleeve W. Check for roll damage.
X. Move the air evacuation hole in the proper position for better results. Y. Adjust the loading plat form.
Z. Loosen knobs on tension blocks.
1. Use two pieces of tape, stick tape on opposite sides of the film and pull apart. 2. Make sure machine is properly grounded.
Shrink Packaging FAQ
1. Will a machine with a Reynolds Sealing System seal Polyolefin?
Many lower profile products (1-4‖) will seal on machines that have a Reynolds sealing system with a
mushroom insert sealing a high quality Polyolefin shrink films. Some very low products (1-2‖) will also seal on a machine with Reynolds sealing system with arrow inserts using high quality Polyolefin shrink films.
2. Will heavy product run on any machine?
Heavy products weighing over say around the 2 to 3 lb. range will need to have special modification made to the conveying systems of that equipment. Some of the heavier products that are larger and spread the weight over a larger area can also be run. The product will have to be tested on the type of equipment that will be used in the production of the product in question.
3. Are Hole punches the only way for air evacuation in a shrink film balloon?
Hole punches have been around for many years and can be still found on many machines. This is not the only way that air evacuation of the shrink film balloon can be accomplished. Pin perforating systems can be
installed on most shrink film unwinds. Although many film companies offers pre-perforated films. These films can be purchased with different configurations of hole patterns depending on the size and configuration of the product being wrapped.
4. What are the advantages of using high quality shrink film?
There are many advantages of using high quality shrink film a quality film will be much more constant. That is to say that the manufactures have good control of the processing of the film. The film formulation from one production of film to the next will be the same. The gauge of the film will be held closer through out the film web. The performance window will be much greater giving the shrink packaging production a much lower rejection rate. The lay flat of the film will also be maintained better. The lay flat of the film is very important for the tracking of film. The shrinking of the shrink film is much more consistent on good quality film which will yield better looking product. The clarity will also be much better.
5. How do I keep light product from slipping on discharge conveyor belt?
Light product sometimes will slip on the discharge conveyor belts causing them to stay in the sealing area or in the discharge area. Check to see that the film in the sealing area is be cut. This can be cause from to low a heat setting, to low a dwell setting, not enough pressure being applied to the seal area, or if using a (hot knife system) the cutting blades may need to be replaced. Then check to see that the film is not sticking to the seal pad. This can be caused by the use of to much heat. Cleaning the Discharge conveyor belt can also help. If everything here is working ok then there is a light product hold down retro kit that can be purchased for many packaging machines. This device pushes down on the product to the conveyor belt to help it drive better.
6. How do I keep the film from sticking to the inverting bars?
Most of the time Shrink films will stick to the inverting bars on packaging equipment because the film has polished the surfaces of the bars that the film runs over. The best way to fix this problem is by either sanding the inverting bars with very fine emery cloth or covering them with mold skin. Mold skin is used for preventing blistering on feet and can be purchased at any pharmacy. Using a harder film sometimes can help as well.
7. How do I keep the film tracking properly?
There are two major reasons for film not tracking properly. The packaging machine is not set up properly or not working properly. First check that the machine set-up is done properly. Check to see that the film is going through the machine evenly that the film webs are under even pressure. Check to see that the film is not under to much tension. Film tension can cause most of the tracking problems on packaging machines. The film web should be taught but not overly tight. Check to see that the film is being driven properly.
The shrink film that is being used has problems. Shrink film can also cause tracking problems. Check to see that the film is not blocked (the film layers should separate with out a lot of pressure). Check to see that the film is laying flat. Check this by unrolling about 10’ of film off the roll and try to hold it in air as tightly as possible. If the film is not flat then there may be a problem with the film. Call your film distributor for help.
8. How can I keep my film from blocking?
Film blocking is generally caused by the film being stored in an area that is to hot. The best way to avoid this is to keep the film in an area that the temperature will not rise above 80 degrees Fahrenheit. Rotating film
inventory can also help.
9. What can I do to keep my film from tearing at the inverting head?
If there is to much film tension then this will cause the film to tear on the inverting head. Check to see the film is being driven properly through the film drive system. Check the film path and make sure that it is clean and free of debris. Also check to see that the film being used is the proper type.
10 .What can I do to keep the film scrap from breaking at the film Puller?
The film is breaking at the film puller because there is possible to much tension on the film web. Check to see that the film drive system is working correctly. Check the film path and make sure that it is clean and free of debris. Check to see that the film is being cut properly at the seal jaw. Check to see that the scrap web is 1 to 3‖ wide depending on film type and quality. Also check to see that the film being used is the proper type.
11. How can I make my shrink packaging look better?
The best ways to improve the look of shrink packaging is to; check to make sure that you’re not making the shrink bag to big. Check to make sure that the air evacuation system is working properly. Check to see that the film seals are complete and strong. Check the Shrink tunnel to see that the proper temperature for the shrink film that is be used is set properly. Check the speed of the conveyor belt going through the tunnel. Check in the shrink tunnel to see that the bag is ballooning and maintaining the balloon until it is just about out of the tunnel. 12. Can I use a shrink film on cold or frozen products?
Shrink film can be used on most any product that is frozen (0 degrees centigrade). To use shrink packaging on frozen product the shrink package balloon has to be held off the product until the last second be for leaving the shrink tunnel. The shrink film will stop shrinking as soon as it touches the frozen product. This will leave the shrink packing appearance looking un-finish and wrinkled.
13. Will the Shrink tunnel melt my product?
Most products will not have any effect to the temperature of the shrink tunnel. If the shrink tunnel is set up properly then the product that is being wrapped will not be in the heat of the shrink tunnel long enough to effect the product. This is because the product does not generally gain more than 10 degrees Fahrenheit when it is in the shrink tunnel.
14. How often should the seal wires be cleaned on a shrink packaging machine?
There are a lot of factors that determine how often seal wires should be cleaned on a shrink packaging machine, here are some of them.
*The type of shrink film being used some shrink films can contaminate seal wires faster than others. *Machine thru put.
*Seal Wire temperature.
Generally if you check them once an hour and you find that the seal wires were not contaminated for say four hours. Then every four hours clean the seal wires. This should help to keep the seals on the shrink package strong.
15. How often should I replace the tapes on seal beads of the shrink sealing machine?
The seal tapes on the sealing beads of shrink packaging machines should be replaced any time that they are starting to look worn, burnt, or cut. The best was to determine how often this should be done is to check the condition of the seal tapes every hour. Then if it takes eight hours for the tape to start to signs of ware then the tapes should be replaced every eight hours.
16. Do I need to clean out inside my shrink tunnel?
The inside of the shrink tunnel needs to be cleaned out on a regular basis. At the end of every shift the tunnel should be inspected for any debris. If anything is found then it should be removed as soon as possible.
17. Does it matter if the tunnel curtains badly worn or missing?
Having badly worn or missing tunnel curtains can make the tunnel temperature vary quite drastically making the quality of the finish shrink package vary. Also having badly worn or missing tunnel curtains will make the tunnel heating system work at lot harder to maintain the temperature setting. This will put a lot of stress on the heating elements and cost a lot more to operate.
18. Why does the shrink tunnel (oven) not come up to temperature?
Some of the reasons that a shrink tunnel will not come up to temperature is because the tunnel curtains are badly worn or missing, the voltage going to the shrink tunnel is to low, or some of the heating elements are not working properly.
19. Why does the shrink tunnel (oven) take so long to come up to temperature?
Some of the reasons that the shrink tunnel temperature is not rising fast is because, the tunnel temperature control system is not working properly, some of the heating elements are not working properly, or the curtains are badly worn or missing. Colder air may be blowing into the tunnel from an outside source.
20. Why is the temperature in the Shrink tunnel (oven) over heating?
The temperature in the shrink tunnel is over heating because the temperature controller or the temperature control system is not working properly.
21. Why is the shrink tunnel (oven) not heating?
The reasons that the shrink tunnel is not heating could be because the heating control system is not
functioning correctly, the heating control system is not turned on, the heating temperature control is set to low, or the heating element is burnt out.
22. Why does shrink film stick together after going through the film separating rod on the shrink packaging sealer?
The reason that the film is sticking together is because the shrink packaging equipment is full of static
electricity. Static charges can build up in shrink packaging equipment because of the shrink film running over the metal rollers and separators on the machine.
23. How do I eliminate static charges from building up in the shrink packaging machine?
The best ways to eliminate static build up in the packaging equipment is to ground the machine to a cold water pipe, ground rod in the ground, or some other metal structure that is grounded. There is also equipment on the market that is available that inject an opposite charge in to film to keep it from sticking together.
24. Why is the film tearing as it goes through the hole perforator?
The possible causes for film tearing as it goes through the hole perforator are: The perforation needles are dull.
The perforation needles are set to deep.
The perforation backing roller is in poor condition. The film that is being used is too hard.
There is not enough film tension on film web.
25. Why is the hole pneumatic hole punch not making a hole?
The possible cause for the pneumatic hole punch to not function properly are: The hole punch die is dull.
The hole punch is not in alignment with die. The air pressure is to low.
The air cylinder is not working properly.
26. Why is the product tearing through the front seal of the shrink film?
Product is tearing through the front seal of the shrink film because the front seal is too weak, or the product is moving faster than the film. Slow down the infeed belt until the film and the product are moving at the same approximate speed.
27. What can I do to keep product from getting stuck in the rollers of the roller conveyor in my shrink tunnel?
To keep product from getting stuck in the rollers of the shrink tunnel adjust the sealer height so the it is just higher than the tunnel height. Adjust the speed of the sealer discharge belt or the speed of the tunnel belt so that the tunnel belt is going slightly faster than the sealer discharge belt. Add additional rollers to the tunnel conveyor belt.
28. How can I keep the Shrink film from curling my thin paper products?
There are special shrink films that are made for product that has trouble with curling. These films have a lower shrink force than other shrink films. Also some times the tunnel setting can be adjusted to help keep the shrink film from curling the thin paper products?
29. How can I keep the shrink film from crushing my product?
If you shrink film is crushing the product you may need to look at shrink film that has a lower shrink force like Cryovac, D935. This type of film has a lower shrink forces than standard shrink films. If you are already using a low force shrink film then try; lowering the tunnel temperature, increasing the tunnel belt speed, or increasing the film containment size. Check the heat evacuation system and make sure that it is working properly.
30. Why is the product getting stuck in the sealing area?
Product may be getting stuck in the sealing area because the product is to light and the discharge belt can not pull it away from the seal jaws. Make sure that the shrink film is being cut and seal completely. Adjust the seal temperature as low as possible but not so low as to keep the shrink film from cutting and sealing. A hold down device may also be needed to push the product down against the discharge belt.
31. Why is the product lifting off the discharge belt when the machine is sealing the film?
Product is lifting off the discharge belt during the sealing cycle because the seal jaw center line is not centered with the product center line. Not having the product center and the sealing center set equally will cause
excessive film tension and make it harder to seal shrink film.
32. Why is the shrink containment on my product so wide?
Shrink containment size is being determined by how wide a containment that the machine is being set for. Adjusting the infeed as close to the film puller or side sealer will help to reduce the containment size. Also adjusting the film to the inverting head so that there is only enough film for the product height.
33. Why is the shrink film containment on my product so long?
Shrink containment size is being determined by how long a containment that the machine is being set for. Adjusting the film prefeed and/or the product placement will help to make the containment smaller. Sometimes adjusting the belt speeds will also help.
34. Why is the product hitting the film puller?
The film is hitting the side sealer because the infeed system is set-up improperly. Move the product further away from the film puller until it is no longer hitting the product.
35. Why is the product hitting the front seal jaw?
Product is hitting the front seal jaw because there is not enough space between the film puller and the product for the height of the product and when the jaw closes it pulls the product into the sealing area. Adjust the infeed to create more space between the film puller and the product.
36. Why is the product hitting the side sealer?
Product is hitting the side sealer because the infeed product guides are not adjusted properly and/or the side sealer is not adjusted properly.
37. Why is the film on my film unwind over spinning?
Most film unwinds have some sort of braking capability. Usually the film is over winding because there is too little tension on the braking system or the braking system is not functional. Inspect the braking system and make sure that it is operational then increase braking tension in small increments until the film roll stops over winding.
38. Why are the film drive rollers on my film unwind not pulling film when they are turning?
Film may not be pulling because there is something keeping the film from unwinding off the film roll. Maybe the film is caught on the separator bar. It’s possible that the drive roller and the pinch roller are not able to come together, check for obstructions or wear. Inspect the condition of the drive roller, it may need to be cleaned or replaced. If the surface has been hardened over time then it should be replaced.
39. Why the air flow in my shrink tunnel (oven) is seem lower than it was before?
Check the air flow path in the shrink tunnel. Inspect the screens of were the air is being draw from inside the tunnel. Check any air flow controls that the tunnel might have. Look for any air restriction that might be causing a blockage in the air flow. Clear any restrictions and test air flow.
40. Why is the film being pulled back into the powered film unwind?
Film is being pulled back into the unwind because either the film has over wound and is under the film roll or the reversing switch is set in the wrong direction.
41. Why is my side sealer not working properly?
Side sealers need to be keep clean and adjusted properly. First check to see if there is any film and/or debris built up inside the side seal unit. Then check the temperature adjustments check to see that they are set correctly for the speed of the machine. There are many types of side sealing units and many different problems that occur if you need further assistance please call.
42. Why is my seal jaw not pulling down tightly on the shrink film?
If the sealing jaw is not pulling down tightly on the shrink film then it might be out of adjustment (automatic and semi-automatic machines). Check to see that all adjustments are made properly. If all adjustment is made properly then check that the system that is pulling the sealing jaws down is working properly (automatic and semi-automatic machines). Check to see that the system that is holding the seal jaw down is adjusted properly (semi-automatics & non-automatics). Also check to see that the seal jaw is contacting the seal pad evenly.
43. Why is my seal jaw opening so slowly?
The reasons that might keep the seal jaw opening slowly are the adjustments in the exhaust restrictors are out of adjustment (over restricted). Check to see that the machine is getting the proper air pressure. Check to see that the air cylinder is functioning properly.
44. Why is my seal jaw closing so quickly?
If the seal jaw is closing to quickly then check to see that the exhaust restrictor are not opened too much. Try closing the exhaust restrictor. If this doesn’t work check the air pressure and the condition of the air cylinder. 45. Why do I hear air leaking out of my air cylinder?
Air cylinders as they start to get worn will start to have air blowing by the seals and causing air leaks. If this is the case then find out which air cylinder is leaking and replace it of repair it if possible.
46. Why do I hear air leaking out of my air valve?
Air valve leaking is a sign of a worn out air valve or a worn out cylinder that has air blowing by seal on the piston. Replace worn devices as needed and test.
47. What can I do to keep my sealer in good working order?
Keeping a sealer in good condition is an every day job. Everyday before the machine is started the machine should be cleaned and inspected. The machine should be cleaned and while cleaning all the sealing, film delivery and conveyor systems should be inspected. If any machine part is showing signs of wear then it should be replaced. Preventative maintenance is the best way to keep the sealing machine in good working order.
48. What can I do to keep my shrink tunnel in good working condition?
Keeping a shrink tunnel in good condition is an every day job. Everyday before the shrink tunnel is started the inside of the tunnel chamber should be cleaned and inspected. The machine should be cleaned and while cleaning the heating and conveying systems should be inspected. If any machine part is showing signs of wear then it should be replaced. Preventative maintenance is the best way to keep the shrink tunnel in good working order.
49. Why is the discharge conveyer on my sealer continuing to coast after the seal jaw has closed? Discharge conveyer coasting is caused be cause braking system is not working properly. Inspect the braking system, check to see that the control system is working properly. Check to see that the brake is working properly.
50. Why is the product getting stuck in the seal jaw and not returning up when the product is in the seal area?
Product is getting stuck in the seal jaws because the seal jaw safety system is not set up properly. Check to see that the jaw safeties are working properly. Check to see that the jaw safety over ride is not coming in to soon. May adjustments as needed and test to see that the system is working properly.
51. Why is the seal jaw coming down to seal, but as soon as it touches the seal pad opens with out making a seal?
When the seal jaw opens as soon as it closes either the dwell time is set too low or the seal jaw safety system is not working properly. First check to see that the jaw dwell time is set properly. This should be (.5 to 5 sec.) depending on film and sealer. Next check to see if the jaw safeties are working properly. Make sure that the film clamps are moving freely; check to see that the safety switches or proxes are sending out an off and on signal to the control system. Check to see if the safety override is set properly. The safety override should come on just be for the seal jaw closes.
52. Why is the Shrink film sticking to my seal jaw on the hot knife sealing system?
Shrink film maybe sticking to the hot knife because the coating on the hot knife has been damaged or the sealing temperature is too high. First check the hot knife condition. Check to see if has been damaged. Check to see if some of the coating has been removed. Then check to see if the sealing temperatures are set to high.
53. Why is the film building up on my hot knife sealing system?
Shrink film maybe building up on the hot knife because the seal bar coating has been worn off. Possibly the temperature is set incorrectly. Some shrink films will not work on hot knife systems.
54. How do I keep the Shrink film from sticking to my seal bars?
The best way to keep Shrink film from sticking to the seal bars is to run the sealing temperature at the proper temperature for the film being used. Also keeping the sealing bars as clean as possible will help to keep film from building up on the seal bars.
55. Why does the sealing temperature have to be set higher than normal?
Sealing temperature may have to be increase due to poor sealing pressure. Check the condition of the sealing pads and seal bars. Check to see that adequate pressure is being applied in the sealing area.